I downloaded ML for my T3i and recorded a timelapse at 24p. The bitrate in Magic Lantern was set at x1.5 which is around 70mbps. I imported the clips into Premiere which took an awful long time to iimport and playback was almost non existant despite using my MSI GT780 laptop with 16GB RAM!

I gather the programme doesn't like these exceptionally high bitrates?

Try using an intermediate codec such as cineform. CS5.5 is a huge leap forward when dealing with native h.264 footage, but you're editing on a laptop with higher bit-rate (ie more bits to process) so you're probably not going to see the full benefits of CS5.5's native editing abilities.

Cineform now has a free program available called GoPro Cineform Studio which you can use to convert your clips. It's more simplistic than their purchased products, but still allows you to convert to the same Cineform codec in either .avi or .mov containers.

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